Surimi
The surimi (すり身 , ''surimi''?) is an ancient technique that was born in Japan due to the need to preserve fresh fish and offer new forms of consumption. The fish is decapitated, gutted, bones and skin are removed, filleted to separate the meat and minced, thus obtaining the fish protein. Surimi is a natural source of fish protein, also highlighting other nutritional properties as a source of omega-3, vitamin B12, vitamin D and selenium.
History
Surimi is a product of Japanese origin appearing in early writings from the year 1115 during the Heian period (790-1180) (1), born from the need to consume fresh fish. The first records of a surimi-derived product refer to kamaboko, which along with other types of products have evolved over the past 900 years. The term surimi comes from the combination of two Japanese words: 'suru' (process) 'mash/mi' (meat), and is defined as myofibrillar fish protein. The concept of the first known surimi product derives from the imitation of the floral part of cattails (genus Typha) resulting in a product called chikuwa. The production of surimi derivatives spread throughout Japan and became part of the diet of the Japanese people during the Edo period (1600-1867).
The process was developed in Japan 900 years ago and is used to make kamaboko. The surimi industrialization process was developed in 1960 by Nishitani Yōsuke of the Hokkaido Experimental Fisheries Institute in Japan with the aim of standardizing the process and achieving greater production efficiency. In the western market it was introduced under the name of chatka, as an imitation of the prized Kamchatka crab (Paralithodes camtschaticus) (2).
The world production of surimi reached 820,000 tons in 2018, remaining stable during 2019 (3). In the European Union, some countries play an important role in surimi market activity with both producing and consuming surimi-derived products. In this sense, France, Lithuania and Spain are the three main producing countries of products derived from surimi and France, Spain, Italy and the United Kingdom as the main consumers of these products.
Raw material
The fish species best considered for making surimi is Alaska pollock (Gadus chalcogrammus), belonging to the cod family. Other species of white fish used in the production of surimi are Pacific hake (Merluccius productus), hoki (Macruronus novaezelandiae) and tropical species such as threadfin bream (Nemipterus spp), big eye snapper (Priacanthus spp), croaker (Pennahia and Johnius spp), lizardfish (Saurida spp), sea bream (Evynnis spp) and ribbon fish (Trichiurus spp).
The quality of surimi can be observed through (1): a) The gel formation capacity, determined with a texturometer b) The color, which the whiter, is associated with higher quality because it comes from the fillets and have a lower level of impurities c) The absence of impurities d) Amount of protein e) Moisture.
Elaboration process
The production process can be carried out both in plants on land and in factory ships at sea. For the production of high quality surimi it is vital to start with very fresh fish. After catching the fish and keeping it at a temperature of 0 °C, after a few hours the decapitation, gutting and removal of bones and skin are carried out. Next, it is filleted, minced and washed with water to remove fat, soluble (sarcoplasmic) proteins, blood,..., with the aim of extracting the myofibrillar protein from the fish muscle. In the next stage, any water that may have absorbed is removed. The extracted fish myofibrillar proteins (mainly actin, myosin and actomyosin) have the functional ability to form thermoreversible gels. To ensure the highest quality and food safety, the surimi is shaped and frozen at -30°C. To guarantee the conservation of the technological properties of the protein at low temperatures, cryoprotective ingredients are incorporated. This intermediate product has exceptional functional characteristics to create and imitate textures, and is used in Japan to make a wide range of traditional products.
Protein quality
Surimi and surimi products, for the most part, provide a total protein content of between 8 g and 15 g per 100 grams of product (4,5,6,7,8), depending on the product, from the species used for its elaboration and depending on the quantity of surimi used for the elaboration of the final product and its category and quality. The Amino acid scoring pattern defined by FAO/WHO (9) proposes reference standards to assess protein quality, taking into account the amount of essential amino acids per gram of protein present in the food, as well as average protein requirements. In this way, it is possible to identify whether the protein in the food is adequate or deficient in some amino acid according to the reference pattern for growth in the case of children and adolescents and the maintenance of human tissues in adults. According to the Amino acid scoring pattern, we observed that the specific amino acid profile of surimi obtains scores above 100 for the 9 essential amino acids (9,10), thus being considered an excellent quality protein. Currently, to determine the protein quality of food or a diet, the European Food Safety Authority (EFSA) refers to the Protein Digestibility-Corrected Amino Acid Score (PDCAAS) as a standard to determine this parameter (11).
The formula to establish the PDCAAS is the following (12): (mg of limiting AA in 1 g of food protein / mg of the same AA contained in the reference protein) x actual fecal digestibility. A good estimate is a mean PDCAAS for surimi and surimi products between 86 and 100, with variability depending on the production system and product quality. Compared to other foods, it could be said that surimi and surimi products have a similar amount of protein as their counterparts such as meat, fish, and eggs. According to European legislation, surimi products can be considered, for the most part, as having a high content or being a source of protein (13).
For all these reasons, surimi protein represents a supply of good quality complete protein, with the presence of essential amino acids in adequate proportions with respect to the needs of the human organism, being in turn well absorbed and used by the digestive system after its consumption and giving rise to the appearance of functional effects in different physiological situations (10).
Nutritional value of surimi and surimi products
Energy contribution and energy density: Surimi and surimi products, according to American (5,6,7), Japanese (14) and Spanish (4) food composition tables, provide between 66 and 115 kcal per 100 g.
According to the classification of energy density for foods suggested in some publications (15) and by the British Nutrition Foundation (16), surimi and its products would enter the category of foods with low energy density, contributing between 0.66 and 1.15 kcal/g.
Protein: Surimi is a natural source of fish protein, since it has an amount of protein similar to that of homologous products such as meat, fish, and eggs (4,5,6, 7,8). See section “Protein quality”.
Fatty acid content and profile: An interesting aspect of surimi products is that the high protein intake, both in quantity and quality, is achieved with a low energy content, partly due to at a very low fat content.
According to the food composition tables (4,5,6,7,14) surimi and surimi products provide between 0.5 g and 4 g of fat per 100 g of product.
Under European legislation (13) some surimi products, containing less than 3 g per 100 g of total fat, could be declared as “low-fat” foods.
Regarding the omega-3 content, surimi and surimi products can be considered, according to current European legislation (13), as a food source of omega-3, as they contain more than 40 mg of EPA +DHA (eicosapentanoic acid and decosahexanoic acid) for every 100 g of product, specifically, 100 mg of EPA+DHA/100 g. EPA and DHA contribute to the normal functioning of the heart (17).
Carbohydrates: According to the sources consulted (4,5,6,7,14), surimi and surimi products provide between 4 g and 15 g of carbohydrates per 100 g of product. This wide range of variability is due to the quality of the surimi, the higher the quality of the raw material, the lower the amount of carbohydrates present. Given its low total carbohydrate intake, the glycemic load of surimi and surimi products is expected to be low (glycemic load less than 10).
Vitamin B12: Surimi is a source of vitamin B12 (4,13), found only in foods of animal origin. The contribution varies between 0.8 to 1.5 µg/100g. Vitamin B12 contributes to the normal functioning of the nervous system and the immune system. It also contributes to the reduction of tiredness and fatigue (17).
Vitamin D: Surimi is a source of vitamin D (13,14), providing between 1-2 µg/100 g. Vitamin D contributes to the normal maintenance of bone and muscle function, to the normal absorption and utilization of calcium and phosphorus, to the normal maintenance of teeth, and to the normal function of the immune system (17).
Selenium: Surimi is a source of selenium (4.13), providing between 10.9 and 28.1 µg/100g. Selenium contributes to the normal function of the immune system, to the normal maintenance of hair and nails, and to the protection of cells from oxidative stress (17).